1. Technical Field
This invention generally relates to vehicles that are capable of being leaned and that have rear steering capabilities, and more specifically to a frame and suspension system that facilitates leaning and rear steering on a vehicle having more than two wheels.
2. Background Art
Vehicles capable of leaning include motorcycles. Of course, standard configuration motorcycles have only two wheels so that leaning the vehicle happens naturally. The benefits of leaning include that leaning facilitates turning. Leaning the motorcycle in a direction while the motorcycle is moving forward actually pulls the front steering in the same direction. Another benefit of leaning the motorcycle is that the wheels are also leaned and better support the forces applied to the wheel and tire. At the same time, leaning increases the contact area of the tire on a driving surface. Still further, leaning the motorcycle better positions the center of gravity on the line of force applied to the surface by the motorcycle and driver.
Rear wheel alignment by a rear steering mechanism has been implemented on vehicles having four wheels, such as automobiles. Rear steering mechanisms have been provided for counter steering the rear wheels for greater maneuverability. These counter steering mechanisms are generally restricted to operation at low speeds.
The present invention relates to a vehicle that includes many of the advantages of a motorcycle on a vehicle having three or more wheels. With the frame and suspensions of the present invention, the same advantages of leaning the wheels and the frame of the vehicle supported on the frame are provided. With each additional wheel over two, an additional adhesion point is provided. Thus, a vehicle with four wheels will have twice as many adhesion points as a standard motorcycle. As such, the vehicle will enable faster stopping. Also, the vehicle can automatically lower the frame and provide a lower center of gravity of the vehicle during deceleration. One way of carrying this out is to automatically cause the rear suspension to mirror the front suspension during braking. Furthermore, it is contemplated that approximately a thirty percent increase in speed around corners may be achieved with the present invention. This is due, in part, to the increased adhesion patch at each of the adhesion points when the wheels are leaned during turning. Still further, with the frame leaning into turns, the centrifugal and gravitational forces are more evenly distributed among the adhesion points. The vehicle can include additional advantages of automatically leaning the frame and wheels and aligning the rear wheels. Aligning the rear wheels reduces drag that typically occurs during turns, and thus improves gas mileage or efficiency in general.
Another advantage provided by the frame and suspension of the present invention is that they include shock absorption by way of shock absorbers and an electro-mechanical tracking mechanism. The term xe2x80x9cshock absorbersxe2x80x9d as used throughout this disclosure can include a spring coiled over a shock absorption device, a torsion bar, or an air shock for example. In any case, it is to be understood that xe2x80x9cshock absorberxe2x80x9d as used herein refers to a mechanism having support characteristics capable of supporting the chassis and body weight of a vehicle and having shock absorbing characteristics. The shock absorption of the frame and suspension can be in addition to shock absorbers on a vehicle body, such as on a motorcycle body. That is, the motorcycle body with its front and rear shocks can be supported on the frame and suspension of the present invention. As can be appreciated this offers redundancy and provides an exceedingly smooth ride. The stiffness of the various shock absorbers and tracking mechanism can be varied to absorb a variety of shock and vibrations.
The shock absorbers of the frame and suspension system of the present invention are mounted as close to a central longitudinal axis as possible. This location together with the structural relationship of the shock absorbers to the frame and suspension provides the advantage of increased mechanical advantage for forces applied to the wheels, the frame, vehicle body, and the driver/rider(s) with increased lean.
The change in position of the shock absorber(s) relative to the lower arm helps reduce the transfer of force to the other side of the frame. Furthermore, the present suspension includes an arm assembly for each wheel that it supports. Each arm assembly can be deflected independently so that the load is minimally transferred to the other side of the frame.
The lean can be effectuated automatically with an electronic control unit (ECU). This enables the system to automatically select the amount of lean based on the speed and angle of turn of the vehicle. Alternatively or additionally, the angle of lean can be determined and automatically adjusted based on feedback from one or more force sensors that are positioned to detect a distribution of gravitational and centrifugal forces. Likewise, the angle of turn of the rear wheels can be automatically adjusted by the ECU. Thus cornering can be significantly aided and the protocol in the ECU can be configured and/or adjusted to place these automatic features at their maximum with a selected safety factor. Alternatively, the ECU can be replaced by other processors including mechanical processors. Such mechanical processors could employ a variety of springs including air springs, and could include compressible and non-compressible fluids to coordinate movement between arm assemblies. Further alternatively, the lean could be effected through a set of gears or a force multiplying device such as a fluid piston, rack and pinion mechanism. Still further, part of the system could be automatic and the rest of the system could be manually controlled by the vehicle driver. In this case, the driver replaces the portion of the processor that would otherwise automatically control at least some of the function of the frame and suspension system. For example, the frame and suspension system could be configured to automatically track a contour of the driving surface for improved shock absorption, while requiring the driver to determine the amount of lean by shifting his or her body weight, as with a standard motorcycle. In this case, the frame and suspension could normally hold the vehicle in an upright position when no substantial leaning force is applied, and lean can depend on the sensory perception and control of the driver.
In an exemplary basic form, a vehicle with a lean and alignment control system in accordance with the present invention includes a frame having a central longitudinal axis. The frame also has an upright axis that is adapted to be generally perpendicular to a surface on which the vehicle rests when the frame is in a neutral position with no net leaning loads applied. A vehicle body is supported on the frame. A suspension comprising a plurality of arm assemblies is connected to the frame. Each arm assembly includes a lower arm having an inboard end and an outboard end, an upper control arm having an inboard end and an outboard end, and an actuator mounted to the lower arm and motively connected to the upper control arm. Many variations are possible without departing from the spirit and scope of the invention. Some of these variations will become apparent in the detailed description below. It is to be understood that while many aspects of the invention are described herein with regard to a vehicle, the invention also encompasses the frame and suspension system by itself. Likewise, the invention encompasses the suspension system and the individual arm assemblies that make up the suspension.
The present invention in one aspect includes a method of properly leaning and aligning a vehicle supported on a suspension. This method has several basic steps including automatically leaning a frame of the vehicle at a predetermined angle relative to an arm of one of a plurality of arms assemblies. Automatically leaning the frame can further include providing a protocol in a processor to control the lean. Data is then automatically fed from a vehicle speed sensor and a steering position sensor to the processor. The frame is automatically moved relative to the arm according to the protocol under processor control.
In another aspect, the present invention includes a method of tracking a contour of a driving surface to absorb shock. The method includes automatically and independently raising and lowering a plurality of arms of a vehicle suspension to accommodate variations in the contour. In order to do this, the system provides feed forward by a mechanical shock absorber. Then the step of raising and lowering the plurality of arms is accomplished by providing feedback to a processor; which raises and lowers the arms under processor control.
The foregoing and other features and advantages of the present invention will be apparent from the following more detailed description of the particular embodiments of the invention, as illustrated in the accompanying drawings.